Procedure for sealing waveguide nozzles

ABSTRACT

Waveguide nozzles are sealed by means of polytetrafluoroethylene strips, whose dimensions correspond with those of the waveguide nozzles to be sealed. The edges of a polytetrafluoroethylene strip are provided with a film of solderable material. The strip is soldered to a waveguide nozzle using said film.

nite States Patent [191 Vlietstra [54] PROCEDURE FOR SEALING WAVEGUIDE NOZZLES [75] Inventor: Jan Vlietstra, l-lengelo, Netherlands [73] Assignee: N.V. ,Hollandse Signaalapparaten,

Hengelo, Netherlands [22] Filed: June 18, 1971 [21] Appl. No.: 154,281

[30] Foreign Application Priority Data July 2, 1970 Netherlands ..7009767 [52] US. Cl ..29/600, 29/473.1, 333/98 R [51] Int. Cl....., ..II0lp 11/00, HOlq 13/00 [58] Field of Search ..29/473.1, 600;

[56] References Cited UNITED STATES PATENTS 2,995,806 8/1961 Allison et a1; ..29/600 3,101,460 8/1963 Walker et al..... ....333/98 P 3,201,296 8/1965 Kilduff et a1 333/98 X 3,210,699 10/1965 Fagano ..333/98 P 3,293,065 12/1966 Roetter 29/473 l X 3,372,471 3/1968 Kuhn ..29/600 3,602,979 9/1971 lacona ..29/473.1

FOREIGN PATENTS OR APPLICATIONS 209,032 7/1956 Australia ..333/98 P OTHER PUBLICATIONS Benderly et al., A Teflon Microwave Window, The Microwave Journal, Vol. 4, No. 3, p. 101-106, March, 1961.

Brown, Charles W., Soldering Hookup Wire Insulated With Teflon Resins, The Journal of Teflon, Vol.3, No.4, April, 1962, pp. 1, 4 and 5.

Hodges, August D., Electroplating Parts of Teflon: It Can Be Done, The Journal of Teflon, May-June, 1967, pp. 4-5.

Primary Examiner-J. Spencer Overholser Assistant ExaminerRonald J. Shore Attorney-Frank R. Trifari [57] ABSTRACT Waveguide nozzles are sealed by means of polytetrafluoroethylene strips, whose dimensions correspond with those of the waveguide nozzles to be sealed. The edges of a polytetrafluoroethylene strip are provided with a film of solderable material. The strip is soldered to a waveguide nozzle using said film.

2 Claims, 1 Drawing Figure PAIENIEnmmzmzs 3 733 6 INVENTOR JAN VL ET T M I I s RA AGENT PROCEDURE FOR SEALING WAVEGUIDE NOZZLES The invention relates to a procedure for sealing waveguide nozzles by means of polytetrafluoroethylene.

Before polytetrafluoroethylene was used to seal waveguide nozzles, they were sealed by means of glass fiber reinforced polyester. However, the use of polyester was disadvantageous in that the sealing was not weatherproof; ultra-violet radiation, for instance, appeared to cause a so-called saponification. This saponification process could be prevented by covering the sealing with a coat of paint. However, since paint has a considerable metaloxide content, a coat of paint would cause additional damping of the energy to be radiated by the waveguide nozzle. Another disadvantage, inherent to a polyester waveguide sealing, is that the waveguide nozzle is unfit to a high degree to be used for transmitting relatively with respect to the dimensions of the waveguide nozzle large high-frequency powers.

it was assumed that the above drawbacks could be prevented merely by sealing the waveguide nozzle in the usual way by means of glass fiber reinforced polytetrafluoroethylene. By in the usual way is meant here the procedure whereby a polyester or polytetrafluoroethylene plate is clamped between two rectangular frames using rubber sealing rings and whereby the pressure window thus formed is screwed to a flange provided at the waveguide nozzle by means of screws.

This procedure, however, has the disadvantage that, when a relatively high power is used, a disruptive discharge will occur at those places where the screws through the two frames and the clamped polyester or polytetrafluoroethylene plate are located, such that the polyester will burn and at a considerably higher power even the polytetrafluoroethylene.

Another disadvantage, inherent to the use of a pressure window and flange as above described, lies in the enlargement of the dimensions of the waveguide nozzle. Such an enlargement disturbs the radiation pattern.

A third disadvantage of the usual sealing method is that leakage will readily occur when gases are used such as freon to reduce the disruptive voltage in waveguide systems.

It is the object of the invention to provide a sealing method for waveguide nozzles which fully obviates the above drawbacks; a method which, moreover, appears to be particularly cheap and requiring little work.

According to the invention waveguide nozzles are sealed by soldering a polytetrafluoroethylene strip, whose dimensions correspond with those of the wave guide nozzle to be'sealed and whose edges are provided with a film of solderable material, to the waveguide nozzle using said frame.

The invention will now be explained more fully with reference to the FlGURE.

In the FIGURE waveguide and waveguide nozzle are denoted by l and 2 respectively. Waveguide nozzle 2 is sealed by means of polytetrafluoroethylene strip 3, whose dimensions correspond with those of the waveguide nozzle to be sealed and whose edges 4 are provided with a film 5 consisting of solderable material. The polytetrafluoroethylene strip 3 is soldered to the waveguide nozzle 2 using said film 5.

Film 5 is constituted by a copper layer which is provided with a lead-tin layer by means of electroplating. The copper under-layer of film 5 can be obtained, starting from polytetrafluoroethylene to which a copper foil is glued and pressed, by removing the central surface by etching.

In view of the fact that the waveguide nozzle is used in an antenna system located at a platform to be stabilized, it is recommended to manufacture the waveguide nozzle from a material that is as light as possible. Therefore, aluminum was chosen as material for the waveguide nozzle. In order to be able to solder polytetrafluoroethylene strip 3 to the waveguide nozzle using film 5, the edge 6 of the waveguide nozzle should be bronzed and then be provided with a lead-tin layer by means of electroplating. If the heavier copper or brass had been chosen as material for the waveguide nozzle, it would have sufficed to apply a lead-tin layer by means of electroplating.

The soldering process proper whereby the polytetrafluoroethylene strip 3 is soldered to waveguide nozzle 2 using film 5 proceeds as follows:

the waveguide nozzle is provided with a soldering flux (resin) and pre-tin plated by immersion in a tin bath of approximately 250C;

soldering flux is applied to the polytetrafluoroethylene strip provided with film 5 and the strip is laid down flat;

the waveguide nozzle is drawn from the tin bath such that the tin can lead off properly; then it is pressed to the polytetrafluoroethylene strip;

after the two parts have fused together and cooled off, the whole is cleaned in a bath, consisting of a mixture of cutting oil, benzene and isopropanol and degreased in freon vapor.

It will be clear that apart from the dip method described here other soldering methods are possible, such as the high-frequency soldering method.

The above described way for sealing waveguide nozzles can also be applied for fitting pressure windows in waveguides. It is known to separate waveguide parts containing gas from waveguide parts lacking this gas, which is done by glueing a plastic partition, such as rexolyte, in the waveguide. It is also known to clamp a mica sheet between two waveguide nozzles provided with flanges and to seal the whole gastight using rubber sealing rings. The difficulties and drawbacks occurring with these known ways are similar to those occurring with the sealing of waveguide nozzles. Here too, a solution is offered by soldering a polytetrafluoroethylene strip, whose edges are provided at both sides with a film of solderable material, to both waveguide nozzles.

What we claim is:

1. A method for sealing a waveguide nozzle by soldering a polytetrafluoroethylene strip having edge dimensions corresponding with confronting dimensions of said waveguide nozzle, comprising forming a copper film along said edges of said polytetrafluoroethylene strip, electroplating a lead-tin layer upon said copper layer, adding solder flux to said lead-tin layer, pretinning the edges of said waveguide nozzle by immersing the same in a tin bath at approximately 250C, removing said waveguide nozzle from said tin bath, allowing the surplus tin to drip off, and pressing the edges of said waveguide nozzle to said polytetrafluoroethylene strip.

2. A method for sealing a waveguide nozzle as waveguide nozzle, comprising bronzing the edges of claimed in claim 1, wherein said waveguide nozzle essaid waveguide nozzle and electroplating said bronzed sentially consists of aluminum and comprises additional edges with a lead-tin layer. steps prior to the step of pre-tinning the edges of said 

2. A method for sealing a waveguide nozzle as claimed in claim 1, wherein said waveguide nozzle essentially consists of aluminum and comprises additional steps prior to the step of pre-tinning the edges of said waveguide nozzle, comprising bronzing the edges of said waveguide nozzle and electroplating said bronzed edges with a lead-tin layer. 